Are these things I should consider bad

[jr_tech]

Originally Posted by TinCanAlley

I was just going to touch the tip of the probe to the hot side and leave the ground clip disconnected.

Good! I just thought that I should pass on a lesson that I learned the hard way. Early 'scopes that I used (Heathkits mostly) were not grounded through the power cord, so I had quite a surprise when I connected my first *grounded* Tek scope to a hot chassis radio!

You likely introduce a bit of error by single tip probing, because the scope earth ground may be a slightly different voltage than the "ground" side of the line. The *best* measurement would be obtained by the 2 tip/2 channel "differential" method, described by dtvmcdonald in a post above. Accurate, and safe for the 'scope

jr

[Username1]

""
Well then I feel better. Now I need to get back into the set to recheck the horizontal sweep as the PP I got put it at 160V and the Sams says it should be 120V. Since the board is driven by the 125V B+, I don't see how it could be putting out a 160V waveform.

""

Is the B+ correct ? are all the B+'s however many there are correct ?
How about B Boost over by the HOT ?

[TinCanAlley]

Originally Posted by Username1

""
Well then I feel better. Now I need to get back into the set to recheck the horizontal sweep as the PP I got put it at 160V and the Sams says it should be 120V. Since the board is driven by the 125V B+, I don't see how it could be putting out a 160V waveform.

""

Is the B+ correct ? are all the B+'s however many there are correct ?
How about B Boost over by the HOT ?

The B+ is at 129V and the B+ Boost is 247 and the same voltages at all their connections points. I'll have to check the other B+s that are in the 20V range. I believe there are two of them (one around 23V and the other around 29V).

[Username1]

as long as those larger ones are under control, don't worry too much about the smaller ones right now.... Stick to the ones you are getting that look too high. tp5.

[TinCanAlley]

Originally Posted by Username1

as long as those larger ones are under control, don't worry too much about the smaller ones right now.... Stick to the ones you are getting that look too high. tp5.

Okay, went after the TP5 again. My DMM has it at 134VAC, but my scope has a PP of 170V. Am I missing something? I guess I'll find some other TPs and see if their voltage matches the waveforms in Sams. If they, then something is wrong with TP5. If they don't, then it's my scope and/or probe or Sams is not accurate.

[TinCanAlley]

With the scope on 50V/Div and putting the probe near the FB, I get this waveform. If you notice, the bottom of the form is ringing the number of jail bars I see on the screen. Is this normal to see this when probing w/out actually making electrical connection to the FB? I get the same form when placing the probe on the collector of the HOT (plastic tip on probe). It's even worse if I go anywhere near the focus wire.

[TinCanAlley]

Originally Posted by Username1

as long as those larger ones are under control, don't worry too much about the smaller ones right now.... Stick to the ones you are getting that look too high. tp5.

Okay, just checked the horizontal pulse which should be 50VPP. I set my scope to 50V/Div and got the noted waveform in Sams as well as a PP of one division. So that one is correct, so the scope seems to be working properly. I've found another TP I'm going to try. It goes to the convergence board and is 170VPP. That should tell me if my scope and/or probe is handling higher voltages correctly.

[TinCanAlley]

Okay, so how do I go about checking my scope for proper AC voltage calibration? I just tested another point that is supposed to be 170VPP. With the scope on 50V/Div I get almost 4.5 divisions. That's almost 225VPP. I checked with my DMM and it reads as 130VAC. I check the one next to it that was supposed to be 20VPP and it showed as 25VPP. The DMM had it as 16.9VAC. I'm pretty sure my DMM isn't showing the exact voltage (everyone keeps writing about RMS and such).

I need to know if there's something wrong with my scope. If so I need to return it to be fixed.

Thanks!

[Username1]

Who makes your dmm, where did you get it, and how much$.

The pins at the horiz board, tp5 is 123, next one down is 124, and bottom is 6. The schematic you posted is not that clear, and gets worse when I blow it up, so If you check the voltages at each one of these points, are they correct, higher, lower?
You need to post "posted" value as in (sams) and actual, (what you read), How DMM Scope.

How about the wave form at the base of the HOT? is it good?

The diode, and cap in the collector circuit closest to the HOT on the schematic? they good?

Does the schematic detail the meter used ? for sams voltage readings?

[andy]

...

[Username1]

Hopefully, this step is completed already..... Remember the scope videos we talked about looking at earlier.

[TinCanAlley]

Originally Posted by andy

The first thing to do is to check the calibrator output on the front of the scope. You should see a perfect square wave with the amplitude specified. If the top and bottom is curved, then adjust the probe (this applies to X10 mode only).

Comparing things to the Sams folder is a bad way to check your scope for accuracy. Sams often have mistakes, many of the circuits in the TV (which isn't working properly) have wide tolerances, and your 465 probably has 10 times the bandwidth as the one Sams used (meaning high frequency signals, and fast pulses will appear larger on your scope).

Yes, the calibrator is 1V and with the probe in 1x and .5V/Div I get a perfect square wave. I then put the probe in 10x and 50m/Div and get another perfect square wave.

See my other post where the 125VAC shows up as 325V on the scope.

[TinCanAlley]

Originally Posted by Username1

Hopefully, this step is completed already..... Remember the scope videos we talked about looking at earlier.

Yes, I've sat though hours of videos including the 2hr+ training. I truly believe I'm doing the settings correctly.

How about I do the horizontal sweep again and when the 170VPP waveform comes up I take a picture of the entire front of the scope so all the settings can be seen?

[TinCanAlley]

Originally Posted by Username1

Who makes your dmm, where did you get it, and how much$.

The pins at the horiz board, tp5 is 123, next one down is 124, and bottom is 6. The schematic you posted is not that clear, and gets worse when I blow it up, so If you check the voltages at each one of these points, are they correct, higher, lower?
You need to post "posted" value as in (sams) and actual, (what you read), How DMM Scope.

How about the wave form at the base of the HOT? is it good?

The diode, and cap in the collector circuit closest to the HOT on the schematic? they good?

Does the schematic detail the meter used ? for sams voltage readings?

My DMM is a Craftsman and is about 13 yrs old. (See pic)

I will check those other points and post their voltage and the Sams voltages.

I was told that the diode on the HOT had to be good since the HOT would be dead if it wasn't. As for the capacitor, I didn't test. Can I use an ESR meter to test it? I believe if I pull the hot, I should be able to test that capacitor without disconnected a leg an it should be pretty much isolated at that point.

I will put the set on her side and remove the bottom to get the waveform of the base of the HOT.

[Username1]

Your camera will adjust to the brightest items, so set the trace very dim, and the graticule very dim as well. You can set the sweep to display one or two cycles of the pulse, just turn the knob to what you want. Set the vert volts/div. so you get close to a full screen, it will be easier to read that way..... you know 3 to 4 divisions is more accurate than say 3/4's of a cm..... or 3/4's division...